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Whats a good gearing for.....

Old 10-14-2008, 12:04 AM
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GreenAce92
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Default Whats a good gearing for.....

Well my brushless esc's died so i have to go and fly on brushed again for some time, so ive got lots of speed 400's lying around, not many of 370's in fact ive only got one that is workin ok but its speeed is rather slow compared to what it should be, ive also got a 380speed, but anyways ive got 2 different SF prop sizes, ive got 8x4.3 and 10x4.7 im trying to figure out what would be the best gearing ratio for a sp 400 or 380 to produce max thrust, i'll most likely use the 10x4.7's just because they should produce more thrust, or maybe i could do a 2:1 gear ratio on the small prop with the sp400 or 380?

what do you guys think?
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Old 10-14-2008, 01:09 AM
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Dr Kiwi
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If those are 6v nominal Speed 400 motors, and you are using 3s.....

A 10x4.7 APC SF will need 4.09:1: that should draw about 8A-9A.

2:1 might be a bit high for an 8x4.3 GWS RS on 3s - 3:1 would keep the amp draw within limits.
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Old 10-14-2008, 02:11 AM
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GreenAce92
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Well actually i was planning on using just nimhs/nicds because my speed controller can run up to 4cells lipo but i broke the little button thing lol which you held for a certain period then programmed which had alittle blue and red light that told you what mode you were in, so i dont want to break my lipos by over drawing them, i wish i ran lipos though lol, oh and about the gearing im using random gears i have and putting them together because i dont even have a pinion gear for a sp 400 motor. Ill see what i can do.

thanks for your help.
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Old 10-14-2008, 04:21 AM
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CHELLIE
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Originally Posted by GreenAce92 View Post
Well actually i was planning on using just nimhs/nicds because my speed controller can run up to 4cells lipo but i broke the little button thing lol which you held for a certain period then programmed which had alittle blue and red light that told you what mode you were in, so i dont want to break my lipos by over drawing them, i wish i ran lipos though lol, oh and about the gearing im using random gears i have and putting them together because i dont even have a pinion gear for a sp 400 motor. Ill see what i can do.

thanks for your help.
Hi GreenAce count the teeth on the pinion gear, and count the teeth on the driven gear (THE BIG GEAR ) divide the number of teeth on the pinion into the number of teeth on the driven gear, and that will give you your ratio, 1-3 , 1-4 etc take care, Chellie
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Old 10-15-2008, 11:34 PM
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GreenAce92
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Oh i know that, im just saying though, i think i have weak motors, because i checked on the rpms produced by the motors online, for example an EM300(standard 370 gearbox motor) produces up to 34k on nimh/nicds no wonder china makes lots of helis on these motors
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Old 10-17-2008, 03:42 AM
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Dr Kiwi
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Originally Posted by GreenAce92 View Post
an EM300(standard 370 gearbox motor) produces up to 34k on nimh/nicds
Well, at 5040Kv, it should manage that, no-load, on less than 7v. Imagine what it does on 8-cells - close to 50,000rpm (as the brushes bounce and commutator gets pitted by arcing)!
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